1. Field of the Invention
Example embodiments of the inventive concept relate to organic light emitting display devices. More particularly, example embodiments of the inventive concept relate to organic light emitting display devices including red, green, blue and white sub-pixels and methods of operating the organic light emitting display devices.
2. Description of the Related Art
An organic light emitting display device implemented using an red, green and blue (RGB) independent deposition method has various advantages, such as low power consumption and a high contrast ratio (CR) characteristic, etc., and thus the RGB independent deposition method has been widely used. In the RGB independent deposition method, patterning for each color of light is performed using fine metal masks. However, the RGB independent deposition method can be hardly applied to a large scale substrate due to precision problems in aligning the fine metal masks and mask sagging phenomenon as the size of masks increases.
A white organic light emitting diode-color filter (WOLED-CF) method using a white organic light emitting diode in conjunction with a color filter has received much attention in consideration of processability and yield. A white organic light emitting diode can be realized by forming a plurality of organic light emitting materials that respectively emit red, green and blue colors in an organic light emitting layer or by forming complementary pairs of organic light emitting materials in an organic light emitting layer. However, in the WOLED-CF method, white light must be filtered through a color filter, and thus the optical transmittance is relatively low when compared to that of the RGB independent deposition method. In order to maximize the optical efficiency, an RGBW pixel structure including a white (W) sub-pixel having no color filter as well as RGB sub-pixels having color filters has been developed.
However, in an organic light emitting display device having the RGBW pixel structure, since a luminance of a W sub-pixel having no color filter is generally twice higher than a sum of luminances of RGB sub-pixels having color filters, a simultaneous contrast phenomenon that a pure color looks darker because of a bright white background may occur. Further, in the organic light emitting display device having the RGBW pixel structure, since the W sub-pixel is driven more than the RGB sub-pixels, a lifetime of the W sub-pixel may be shorter than that of each RGB sub-pixel, which results in a decrease of a lifetime of the organic light emitting display device.